For gas utilities, there are several system integrity activities that are labor intensive and expensive to perform. Cathodic protection is an industry standard method to prevent buried iron or steel structures (pipes, foundations, etc.) from corrosion. When properly protected, the ferrous metal ceases to corrode, and will last indefinitely. Cathodic protection involves placing a slight negative potential (for example, −0.8 to −1.2 VDC), to the protected metal, with respect to the surrounding ground. Generally speaking, cathodic protection can be either passive, employing sacrificial buried anodes, or active, using transformers and rectifiers. Further general information relating to cathodic protection is readily available and thus will not be further discussed herein as it forms no particular aspect of the present subject matter.
The gas industry uses cathodic protection extensively to protect buried iron/steel pipes from corrosion. Due to the inherent safety issues related to the distribution of flammable gas, under present regulatory conditions, the Department of Transportation (DOT) requires gas utilities to inspect the condition of their cathodic protection system and report on it at least on an annual basis. A utility maintenance department is also generally concerned with cathodic protection as it prevents the long term deterioration of the pipes.
Cathodic protection systems can become compromised when the potential between the surrounding earth and the protected structure becomes too small. Such event can occur with the failure of the anodes, or transformers/rectifiers, which provide the potential, as well as failure of ground beds associated with the generation of the protecting potential. In addition, the protection can be compromised when the insulation between the pipe and grounded structures fails. Such can be a physical insulator failure, or can be when a grounded structure touches the protected structure, for example, in an instance where a water pipe crosses a protected gas pipe, or a metal dog leash, etc. is attached to a protected pipe, and becomes grounded.
Once the cathodic protection is compromised, the protected structure begins to deteriorate as rust begins to pit the structure. Such deterioration is irreversible, and can eventually lead to failure of the structure (resulting in, for example, a gas leak). Prompt recognition and attention to problems related to a compromised cathodic protection system can save expensive repairs from being required, and can help identify the cause of the failure, before vegetation, construction, or other intervening events covers up the source.
Utility companies for regulatory compliance must periodically measure the potential between the surrounding ground and the protected structure. For example, a voltmeter can be used to measure such potential, which must exist within the range of −0.8 VDC and −1.2 VDC in order to provide most complete protection. During pipe burial, test stations are installed to provide access to the potential of the protected structure, and a portable or permanent ground reference provides the potential of the surrounding ground. As well understood by those of ordinary skill in the art, the associated volt meter or similar device is placed between such two potentials in order to determine the difference.
Test stations may typically be situated in locations where there is little access to power. Such fact typically prevents the use of a line powered monitoring system. A battery based monitoring system would have limited life, and require some maintenance. Due to the cost of developing a suitable battery based system, the industry essentially has had to utilize an expensive manual process.
U.S. Patent Application Publication 2008/0177678 A1 to DiMartini et al. discloses a method described as communicating between a utility and its customer locations. U.S. Patent Application Publication 2006/0031180 A1 to Tamarkin et al. describes integrated metrology systems and information and control apparatus for interaction with integrated metrology systems. U.S. Pat. No. 7,069,161 B2 to Gristina et al. discloses a system described as managing resource infrastructure and resource consumption in real time. The complete disclosures of all United States Published Patent Applications and Patents mentioned herein are fully incorporated herein by reference for all purposes. An article by David J. Southern “Operators Extend SCADA Investment to Vital Cathodic Protection” in the June/July 2008 issue of Remote Site & Equipment Management describes the possible integration of a frequency hopping spread spectrum cathodic protection remote monitoring device into an existing Supervisory Control and Data Acquisition (SCADA) infrastructure.
While various implementations of telemetry systems have been developed, and while various integrated metrology systems have been developed, no design has emerged that generally encompasses all of the desired characteristics as hereafter presented in accordance with the subject technology.